The role of NAD ion and NAD ion analogs in the stimulation and inhibition of the initiation step of protein synthesis has been studied by four independent assays. NAD ion up to 0.16 mM stimulates protein synthesis. At concentrations greater than 0.16 mM, NAD is inhibitory. The stimulatory and the inhibitory effects of NAD ion occur at the initiation step. The inhibition observed with 1.5 and 4.0 mM NAD ion is reveresed by the high salt ribosomal wash protein fraction. The effect of NAD ion analogs, 2'dNAD ion, and 3'dNAD on the ADP-ribosylation of nuclei isolated from rat liver shows that 0.5 mM 2'dNAD and 3'dNAD inhibit DNA synthesis 10-fold greater than NAD. In addition, the chain length with 2'NAD and 3'NAD is 1.2-1.3; the chain length for NAD ion is about 10. Finally, 2'dNAD results in a new 1"--3' osidic linkage. The effect of 3'dNAD on E. coli and mouse myeloma RNA polymerase II has been studied. (alpha-32P)3'dATP and (3H)3'dATP are incorporated into the 3' end of RNA. 3'ATP also inhibits the elongation step in RNA synthesis. Six NAD ion analogs, modified in the adenine and adenine ribose, clearly show that the 2'- and 3'-hydroxyl groups of NAD ion are essential for productive complex formation in the dehydrogenases. The biosynthesis of the 1,3-oxazine ring of minimycin shows that carbons 4 and 5 of glutamic acid is the two carbon donor for carbons 4 and 5 of the oxazine ring. L-Leucine is the six-carbon precursor for the heterocyclic ring, 3-ethylidene-L-azetidine-2-carboxylic acid, of the polyoxins.